None wrote:
Hello,

Basically we have a bacterial slime build up along our rising main,
which, when it flares up, makes our water slimy and horrible to wash
in/drink etc. It probably happened some years ago when the house was
left idle, ie stagnation occurred. The only thing that temporarily
helps is turning off the water at the outside stopcock, and back on
again after opening the garden tap. The water flows through at full
whack, and this clears the problem, albeit only for a few days...

Should I replace the whole rising main, or come up with something a
little more cost effective? Its doing me nut.

I need more information to understand what is going on. What do you mean
by a rising main? Is this from a public or private supply? If from
public, there should be sufficient disinfection to prevent bacterial
growth in the supply pipe. That you mention a stopcock suggests a public
supply - but not necessarily the case. I'm loath to provide advice
without a better picture of your situation.

Replacing the rising main would do nothing, if you have a continued
supply water quality problem. More info. please.